1. Field of the Invention
A method used in a wireless communication system and related communication device are provided, and more particularly to, a method of handling multimedia broadcast multicast service (MBMS) data reception on multiple component carriers in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) for communicating with a plurality of user equipments (UEs) and communicates with a core network including a mobility management entity (MME), serving gateway, etc for NAS (Non Access Stratum) control.
A long term evolution-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system, considering relaying for cost-effective throughput enhancement and coverage extension. For example, a relay can be deployed at the cell edge where the eNB is unable to provide required radio quality/throughput for the UEs or at certain location where radio signals of the eNB cannot cover. The LTE-A system can support a wider bandwidth up to 100 MHz to satisfy requirement for peak data rate. A carrier aggregation where two or more component carriers are aggregated is employed for the LTE-A system to achieve wider-band transmission. An LTE-A specification supports carrier aggregation for both continuous and non-continuous component carrier with each component carrier limited to a maximum of 110 resource blocks. The carrier aggregation increases spectrum flexibility by aggregating the component carriers in the different frequency band (non-continuous spectrum).
Since the delivery of identical content to multiple users via uni-cast transmission (bidirectional point-to-point transmission between the network and each of the multiple users) is a very inefficient method of transmission, a multimedia broadcast multicast service (MBMS) service may be introduced in LTE-A specification to give the opportunity to broadcast TV, film, information such as free overnight transmission of newspaper in digital form and other media in these networks. Compared with the uni-cast transmission, the MBMS service is a downlink only and point to multipoint connection from the network to multiple users or a specific group of the users. The broadcast capability of the MBMS service enables to reach unlimited number of users with constant network load. Further, the MBMS also enables the possibility to broadcast information simultaneously to many cellular subscribers.
Two important scenarios have been identified for the MBMS service. One is single-cell broadcast, and the second is MBMS Single frequency network (MBSFN). MBSFN is envisaged for delivering services such as Mobile TV, using the LTE infrastructure. In MBSFN the transmission happens from a tightly time-synchronized set of eNBs, using the same resource block. A UE receiver will therefore observe multiple versions of the signal with different delays due to the multi-cell transmission. Since the transmissions from the multiple cells are sufficiently tightly synchronized for each transmission to arrive at the UE, this makes the MBSFN transmission appear to the UE as a transmission from a single large cell, and the UE receiver may treat the multi-cell transmission in the same way as multi-path components of a single cell transmission without incurring any additional complexity.
The MBMS service was provided either on a dedicated carrier in which all subframes are used for MBSFN transmission, or on a mixed MBSFN/uni-cast carrier which is shared between MBMS and uni-cast service. Besides, the network transmits the same MBMS service data both in the dedicated carrier and the mixed MBSFN/uni-cast carrier for UEs with different releases (e.g. 3GPP specification rel.10 and Rel.9) since UEs with certain release do not support the dedicated carrier. However, for the UEs capable of supporting the dedicated carrier and the mixed MBSFN/uni-cast carrier, receiving the same MBMS data on both two component carrier causes power consumption.